Involvement of the calcium-specific protease, calpain, in the fertilizing capacity of human spermatozoa.

We recently reported the novel finding that human spermatozoa contain the calcium (Ca2+)-dependent protease, calpain. In somatic cells this protease mediates several cellular activities regulated by Ca2+ including membrane fusibility during cell-to-cell interactions. In this paper we examined the participation of sperm calpain in sperm-oocyte penetration, a process that is dependent on Ca2+ and involves membrane fusion between the two cells.

Changes in expression of adenyl cyclase activity in human endometrium during hormone replacement therapy and ovarian stimulation.

We have investigated membrane fractions prepared from human endometrium for activity of the signalling adenyl cyclase (AC). We characterized the AC guanine nucleotide-binding proteins (G proteins) and examined the changes in AC activity during evaluation cycles of oestrogen and progesterone replacement therapy as well during ovarian stimulation cycles. AC activity was determined by the conversion of substrate ATP into cyclic AMP under basal conditions and in the presence of guanine nucleotide or forskolin.

Calpain-calpastatin: a novel, complete calcium-dependent protease system in human spermatozoa.

Calpain, a calcium (Ca2+)-activated cysteine protease presents in several somatic mammalian cells, has been demonstrated to mediate specific Ca2+-dependent reactions including cell fusion. Because spermatozoa cells have an absolute Ca2+ requirement for penetration of oocytes, we have postulated that calpain would also be found in mammalian spermatozoa. Here we show that whole sperm homogenate and cell fractions prepared from ejaculated human spermatozoa contain calpain activity.

Enzymatic amplification of specific deoxyribonucleic acid sequences from single cells: evaluation of a simplified and rapid method for use in preimplantation genetic diagnosis.

Objective: To develop a simplified polymerase chain reaction (PCR) protocol on single cells for the purpose of preimplantation genetic diagnosis. Also to evaluate a new thermal cycler, RoboCycler 40 (Stratagene, La Jolla, CA), for reducing the time to complete PCR amplification.

Design: PCR amplification without DNA purification or reamplification of a 149 base pair (bp) segment of the human Y chromosome was used as a model.

Status of hCG/LH receptor and G proteins in human endometrium during artificial cycles of hormone replacement therapy.

Objectives: We examined the existence of hCG/LH receptors and associated GTP-binding (G) proteins in membrane fractions of nonpregnant human endometrium and investigated whether their expression is affected, in vivo, by estrogen and progesterone replacement therapy.

Methods: A pool of normal endometrial biopsy specimens (n = 5) was initially used to characterize receptors and G proteins. Subsequently, biopsy specimens (n = 22) were obtained from 11 patients undergoing evaluation cycles of hormone replacement therapy (HRT).